Solar heating for greenhouses.

Hi friends, have any of you installed and got working a solar heating system for your greenhouse?
I am very interested in this, basically first you dig a large hole in the ground in the green house, insulate the hole , fill it with a heat retaining product eg old bricks from a storage heater, install a small chimney and cover the hole.
A solar panel is used to (via a battery) drive a 12v dc fan, it pumps the hot air from the top of the greenhouse (through a plastic pipe) to the base of the heatsink (hole in ground) this heats up the bricks during the day. During the night the pump pushes cool air from the green house into the heatsink which through a small chimney pushes out the stored heat.
Hoped you followed it – I found the idea just googling greenhouse solar heating. The cost doesn’t seem too high and on the coldest of nights, or very dull overcast days I’ll use my old paraffin heater.
I’ve just got to persuade OH to go along with the ‘little’ project.
If any of you have done something similar I’m all ears.
Kay.

Comments

Who knows, one day we'll all have to do it ! I find it fascinating, and not just cos I like saving money :-) In my case it's not practical as firstly I'm too old lol, secondly the herringbone from my septic tank runs beneath the GH.

I get confused when watching TV programmes about such things as they tend not to concentrate on the issue, more on the characters. It's a great concept though, imagine free heat with almost nothing to do. I know someone who has bought a new house and the first job was to dig up the garden and install an underground heat source supply, also free.

I empathize with you there Wagger, The only good thing about TV today is that it's so mind-dumming that it encourages you to get on with you're own life, we'd wouldn't have a life of our own if it was good all the time.:-)))

Heron - in principle it should work , have a look a maplins webstie for solar panels and fans.
So if the sun pops out the solar panel produces 12v and the fan does the business, the sun goes in and the power output is reduced. -the fan slows or stops - there is no need for a battery as you don't need a constnt supply could it be that simple?

Yes i did build the solar powered heat sink dick strawbridge made the hardest thing is digging the hole .I found that you needed a more beefy fan than the one he used for it to be effective .well worth doing but i would suggest a better way would be to use the whole of the greenhouse subsoil floor a lot more work but i think this idea works see link www.sunnyjohn.compersonal
choice.
References
1 www.sunnyjohn.com
2 www.roperld.com/science/
YMCAsolargreenhouse.htm
Andrew Collins actually built a solar system in a 12x8 greenhouse and managed to maintain a resonable and constant temp very difficult in a glass house.